[Elecraft] Wiring 101: I solved it, but why?

[Tim]

Hi Don and fellow Elecrafters -
  I went over my power cord with a fine tooth come and I finally noticed
that one of the insertable tabs on the Anderson Power Pole was not quite all
the way in. You may recall that the manual says to be careful about getting
solder on the tongue of this tab. The reason is that it can cause the tab to
appear to lock in the right position yet not be fully engaged. In this case
the inserted tab was probably recessed 1/8" too much. I took the power pole
off and and made up a new one - being more careful about the soldering. That
solved the problem.
  But what was happening there? The voltage was getting through enough to
turn on the K2 - but the tab not fully connecting somehow caused the hum.
Anyone know how that works? BTW the power supply is not a switcher - its an
Astron linear (which by the way has always had a slightly annoying quiet hum
or vibration in the P/S itself  - which I think all Astrons have?).
  Thanks folks!
73/Tim NZ7C
----- Original Message -----
From: "Don Wilhelm" <w3fpr@peoplepc.com>
To: "Tim" <nz7c@cox.net>; "Elecraft Reflector" <elecraft@mailman.qth.net>
Sent: Saturday, September 13, 2003 2:23 PM
Subject: Re: [Elecraft] Wiring 101 question


> Tim,
>
> Your question may not be as elementary as you surmise.
>
> My guess (and it is only a guess) is that your power supply is the cause
of
> the 'noise'.  I would wager that you have a switcher supply there, and the
> effective length of your new power cord that you stumbled on may be the
> right length for some noise generating circuits in the supply to radiate.
>
> Actually it could be any number of things - all related to the power
supply
> capabilities.  Oscillations can happen even with power wiring - rare, but
> possible, or you may be creating just the right ground loop for strange
> things to happen.
>
> Describe for us your power supply particulars and the entire power wiring
> stucture including any grounding wires and perhaps we can offer better
help.
>
> 73,
> Don W3FPR
>
> ----- Original Message -----
>
> | Hi folks -
> |   The nice thing about this reflector is that nobody calls you an idiot
> when
> | you ask REALLY simple questions - at least so far hi hi!
> |   So here is the simple question. I just made a second power cord for my
> | K2/100 so that I could locate the antenna tuner on a different shelf
> rather
> | than right under the K2/100.
> |   Both the old and new cord have a "Y" joint which takes power from the
> main
> | lcord and runs it to the ATU. The second power cord has a much longer
ATU
> | line though. It's about 6 feet long. There is a "Y" joint about 2 feet
> from
> | the radio end of the cable and the fuse is about a foot from the
opposite
> | end. The ATU cord length is about 2 feet. Before plugging this new cable
> in
> | I checked the voltage at the radio and and on the ATU jack end - all was
> | fine. Also tested for any shorts - all was fine. The problem is that
when
> I
> | turn on the rig with this power cord I get a loud noisey, steady hum -
> which
> | made me turn the rig off immediately. It occurs regardless of whether
the
> | ATU section is plugged into the ATU. When I put the original power cable
> | back on and no problem.
> |   I'm just a solder jockey that could not troubleshoot his way out of a
> | paper bag - but the cable delivers proper voltage and has no shorts -
fuse
> | is OK - what could I have done wrong? How can I determine the cause of
> this
> | kind of issue? Thanks for any help folks!
> | 73/Tim NZ7C
>
>
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